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PubMed1976

Motor reactions during the antenatal period correlated with the periodic change in the activity of the cardiovascular system.

A connection between the periodic appearance of vagal bradycardia and of intrauterine large-amplitude respiratory movements, as well as the appearance of generalized jerky-type and more sustained extensor motor reactions, has been established in experiments on dog fetuses connected with the mother through the umbilical cord. Brief vagal bradycardia also arises immediately after completion of these reactions and is an analogue of the vagal phase in adults after motor activity. These correlated phenomena are caused by periodic reversible mild hypoxemia which through the chemoreceptors of the sinocarotid zone stimulates the centers of vagal innervation of the heart and the centers of innervation of skeletal muscles. These phenomena disappear when the mother inhales a gas mixture containing less than 14-15% oxygen or greater than 50-60% oxygen, as well as when the mother is under deep anesthesia.

Animals↗
PubMed1980

A new computer technique for continuous measurement of the pre-ejection period in the human fetus: physiologic significance of pre-ejection period patterns.

A new interactive computer graphics system was developed for continuous online or offline measurement of the pre-ejection period (PEP) in the human fetus during both the antepartum and the intrapartum period. A significant feature is the system's ability to accurately measure PEP from the onset of QRS complex to the beginning of aortic opening with a resolution of less than 2 milliseconds. Normal patterns of PEP prolongation were observed with fetal movement and occlusion of the umbilical cord, whereas progressive shortening of PEP was noticed with late decelerations associated with acute hypoxia. A pathologic pattern of PEP prolongation associated with late decelarations and poor heart rate variability was observed with chronic hypoxia and acidosis. These patterns suggest that continuous monitoring of PEP may be a useful adjunct to current monitoring methods when attempting to assess fetal cardiac performance and well-being.

Computers↗
PubMed1983

Partial elimination of G1 and G2 periods in higher plant cells by increasing the S period.

Meristematic cells from Allium cepa L roots can attain a steady-state of growth at both 15 and 25 degrees C in the presence of drugs, hydroxyurea and 5-amino-uracil, which reduce the rate of DNA synthesis. These drugs, at used concentrations, significantly lengthen the S period without altering the cell growth rate, as indicated by the maintenance of the generation time. It has been observed that steady-state populations respond to a gradual increase in S by a reduction of G2 until a minimum value; with larger lengthening of S, both G1 and G2 are reduced. Natural synchronous populations have been used to study cell cycle parameters during transition from the physiological steady-state to the new one created by the presence of the drug. G2 (but not G1) is reduced during transition even in the presence of maximum drug concentrations that do not alter the cell growth rate. Both the S period and the division time are lengthened during transition. These observations support the concept that certain fractions of G1 and G2 are expendable, because they have no role in the DNA-division sequence of cell cycle events. We conclude that cell size regulates the length of these fractions by means of a negative correlation.

Cell Cycle↗
PubMed1991

The use of conditional probabilities to examine age-period-cohort data: further evidence for a period effect in major depressive disorder.

There is growing evidence that rates of major depression have been increasing over this century, with successive birth cohorts showing increased lifetime risks and earlier ages of onset. In this paper, we describe and compare onset rates in six birth cohorts of first degree relatives of probands with affective disorders from the NIMH Collaborative Study, using graphs of conditional probabilities of first onset. There is evidence of a period effect and age-period interaction for both men and women.

Adult↗
PubMed2005

Fertility and hatchability of eggs laid in the pullet-to-breeder transition period and in the initial production period.

The initial eggs produced by broiler breeder hens are relatively small compared with later in the production cycle. An evaluation of indices related to hatchability is required when these eggs are to be used for the production of broiler chicks. Two experiments were conducted to evaluate characteristics related to the hatchability of eggs from pullet-to-breeder transition phase, at 25 and 27 weeks of age, and from the peak of production period and five weeks later, at 32 and 37 weeks of age. Eggs from birds 25 weeks had a lesser fertility in Experiment 1. Mortality occurred unevenly in early (1-5 days), middle (6-17 days) and late (18-21 days) incubation, and greater mortality was observed after the internal membrane was ruptured. The younger the hen, the lighter the egg, chick, and shell, and the longer the time required to complete the hatching process. In Experiment 2, greater mortalities were observed at the early period (1-5 days) and after "pipping" of the internal and external membranes. Embryos from heavy eggs of breeder hens 37 weeks of age took less time to complete the hatching process. Results indicated the larger the egg, the heavier the chick and shell, and the lesser the shell percentage. As breeder age advanced, characteristics related to egg fertility and hatchability improved.

Aging↗
PubMed2006

Periodic leg movements in sleep and periodic limb movement disorder: prevalence, clinical significance and treatment.

Periodic leg movements in sleep (PLMS) are a frequent finding in polysomnography. The prevalence of PLMS is estimated to be 4-11% in adults. In childhood, PLMS rarely occur although medical conditions like sleep apnea syndrome or neuropsychiatric disorders can lead to high rates of PLMS. In the elderly, PLMS are also common in subjects without sleep disturbances. In sleep studies, PLMS are found most frequently in restless legs syndrome (RLS) and often occur in narcolepsy, sleep apnea syndrome and REM sleep behavior disorder. Some patients with otherwise unexplained insomnia or hypersomnia reveal an elevated number of PLMS, a condition defined as periodic limb movement disorder (PLMD). PLMS were found also in various medical and neurological disorders that do not primarily affect sleep. A summary of these is presented. In sleep disorders related to dopaminergic dysfunction such as RLS, PLMS are considered to be a symptom of the disease. In other disorders like primary insomnia, the clinical relevance of PLMS is still being controversially discussed. Studies with findings both pro and contra are referred. To date, only a few studies have evaluated the efficacy of therapeutic substances in reducing PLMS in PLMD patients. Their results need to be confirmed in controlled randomized trials.

Aged↗
PubMed2003

Novel route to periodic mesoporous aminosilicas, PMAs: ammonolysis of periodic mesoporous organosilicas.

A new route to periodic mesoporous aminosilicas (PMAs) that contain amine functional groups in the framework of a mesoporous network is reported. The materials are prepared via thermal ammonolysis of periodic mesoporous organosilicas (PMOs) under a flow of ammonia gas. PMOs integrate similar or even higher quantities of nitrogen-containing groups upon ammonolysis than similarly treated ordered mesoporous silicas (MCM-41). The quantity of amine groups introduced into the materials was found to depend strongly on the ammonolysis temperature. The largest loading of amine groups was obtained when a well-ordered cubic methylene PMO material without prior vacuum-drying was thermolyzed in ammonia. The ordered mesoporosity of PMOs was preserved during the ammonolysis with only a slight decrease in the mesopore size and the degree of mesostructural ordering. The extent of substitution of framework oxygen by amine and nitride groups was established by solid-state (29)Si CP-MAS, (29)Si MAS, (15)N MAS, and (13)C CP-MAS NMR spectroscopies, elemental analysis, and X-ray photoelectron spectroscopy. In some cases, methylene and methyl functional groups were also present in the PMAs along with amine functional groups, as inferred from elemental analysis and gas adsorption, particularly in cases where PMOs were subjected to ammonolysis at 400 and 550 degrees C for several hours. This resulted in new multifunctional mesoporous organoaminosilica nanomaterials with properties that could be tuned by systematically varying the relative amounts of hydrophilic amine and hydrophobic hydrocarbon pendent and framework groups. The stability upon storage was found to be much higher for PMAs obtained from PMOs than for those obtained from MCM-41 silicas under the same conditions.

Journal Article↗
PubMed2007

Enforcing periodic secondary structures in hybrid peptides: a novel hybrid foldamer containing periodic gamma-turn motifs.

This note describes the design, synthesis, and conformational studies of a novel hybrid foldamer that adopts a definite compact, three-dimensional structure determined by a combined effect of the special conformational properties of the foldamer constituents. The striking feature of this de novo designed foldamer is its ability to display periodic gamma-turn conformations stabilized by intramolecular hydrogen bonds. Conformational investigations by single-crystal X-ray studies, solution-state NMR, and ab initio MO theory at the HF/6-31G* level strongly support the prevalence of gamma-turn motifs in both the di- and tetrapeptide foldamers, which are presumably stabilized by bifurcated hydrogen bonds in the solid and solution states. The strategy disclosed herein for the construction of hybrid foldamers with periodic gamma-turn motifs has the potential to significantly augment the conformational space available for foldamer design with diverse backbone structures and conformations.

Amino Acid Motifs↗
PubMed2003

Respiratory activity of bulbospinal preparations from newborn rats subjected to periodic hypercapnia in the prenatal period.

Periodic exposure of pregnant rats to hypercapnia (10% CO(2)) delayed the development of mechanisms underlying respiratory rhythmogenesis in newborn animals during the early postnatal period. In vitro studies showed that rhythmic activity of the respiratory center in newborn rats (days 0-3) was 2-3-fold lower than that in intact preparations. Age-related changes of respiratory activity were absent, while the reactions of the respiratory center to CO(2) were suppressed compared to the control.

Age Factors↗
PubMed1989

Comparison of period-by-period fundamental frequency of stutterers and nonstutterers over repeated utterances.

The fundamental frequency (f phi) of the first five periods in the acoustic wave form of vowels following stop consonant productions and the f phi of a period approximately 100 ms into the vowel were analyzed in the repeated fluent utterances of 10 nonstutterers and 10 stutterers both pre- and posttherapy. Group data indicate that the nonstutterers and stutterers showed similar f phi diminution patterns in vowels immediately following stop consonants. Additionally, the stutterers were not significantly different from the nonstutterers in their ability to achieve a stable f phi over repeated utterances. These results are discussed with respect to a previous analysis of the present data (Sacco & Metz, 1986) in which it was found that stutterers were significantly more variable than nonstutterers in their ability to achieve a stable f phi over repeated utterances. It is suggested that stutterings in the immediate vicinity of otherwise fluently produced words may influence certain production characteristics of those words.

Adult↗
PubMed1981

Most of the G1 period in hamster cells is eliminated by lengthening the S period.

Two Chinese hamster cell lines, G1+-1 and CHO, have been grown in the presence of low concentrations of hydroxyurea to determine how a slowing DNA synthesis (i.e., a lengthening of the S period) affects the length of the G1 period. Hydroxyurea concentrations of approximately 10 microM do not alter the generation times of these cell lines but do cause increases in S with corresponding decreases in G1. In both cell lines, 10 microM hydroxyurea reduces G1 to an absolute value of 1 hr, which represents decreases of 70% (G1+-1) and 60% (CHO) from control values. Higher concentrations of hydroxyurea increase the generation times and lengths of S for both cell lines but do not reduce G1 below the minimum value of 1 hr. These observations indicate that the majority of G1 is expendable and most of G1 therefore cannot contain specific events required for the initiation of DNA synthesis. This result supports the hypothesis that G1 is a portion of the cell growth cycle but not of the chromosome cycle.

Animals↗
PubMed1975

[Substitution of protein feed through lysine-supplemented high-protein wheat during the breeding and laying period of hens. 1. Problems, analytical methods used and results obtained in the chick period].

Different parameters were investigated in a trial carried out for the 8-week chick period with an experimental group receiving a protein feed in which 7% of the feed, relative to that of the control group, was replaced by protein-rich wheat. Values for consumption were higher in the controls than in the experimental chicks because of the lower energy content of the ration. Statistically well-established data were obtained indicating that the amounts of crude protein, lysine and sulfur-containing amino acids consumed per unit of weight gain were lower in the experimental group than in the control group. Total body analyses showed that the bodies of the control birds contained more crude protein (alpha less than 0.05) and less fat (alpha less than 0.001). The rate of mortality during the 8-week chick period was 1.1% in the control group and 0.5% in the experimental group.

Animal Feed↗
PubMed1976

[The substitution of lysine supplemented high protein wheat for protein feeds during the rearing and laying periods of hens. 8. Nitrogen excretion and true amino acid digestibility as an effect of various lysine levels and successive laying periods].

Digestibility trials were performed with laying hens receiving 3 types of rations containing equal proportions of the same dietary components. The percentage of high-protein wheat in these rations was 74%. Ration I was supplemented with 0.12% lysine while 0.06% lysine was added to ration II; ration III remained unsupplemented. The crude protein content of rations 1 to 3 was 16.1%, 16.5% and 16.6%, respectively. The corresponding lysine percentages were 0.66, 0.62 and 0.56. Studies were made to investigate the influence of different lysine levels on the rate of N excretion and various amino acid data. These studies were carried out during two successive laying periods. Only random differences between the data for urinary N excretion and N balances per kg liveweight were obtained in the two laying periods and for the different lysine levels. The true lysine digestibility was significantly lower in the poor-lysine ration as compared with the ration with 0.66% lysine. Moreover, the absorptive capacity for thio-amino acids is influenced by the lysine level of the ration. The proportion of lysine contained in faecal crude protein increased with the decreasing lysine content of the ration. Similarly, the total number of amino acids present in faecal crude protein increased with the declining supply of lysine. These findings suggest that relatively more NPN compounds are excreted in the faeces if adequate amounts of amino acids are supplied rather than when one amino acid is deficient.

Amino Acids↗
PubMed2001

Resonant effects in periodic gratings comprising a finite number of grooves in each period.

We give numerical evidence of a kind of resonance that appears in infinite perfectly conducting gratings comprising a finite number of grooves in each period when illuminated by a normally incident p-polarized plane wave. This phenomenon is intimately connected with the particular distribution of the phase of the electromagnetic field inside the cavities, which is automatically generated by waves of certain resonant wavelengths. The resonances appear as sharp peaks in the specularly reflected efficiency and are accompanied by a significant intensification of the interior field. We study the particular case of rectangular cavities and consider configurations with different numbers of grooves per period. The diffraction problem is solved for s and p polarization by using the modal method, which proves to be especially suitable for this profile.

Journal Article↗
PubMed2003

Noise-induced fluctuations of period lengths of stable periodic orbits.

We discuss a class of one-dimensional maps, which possesses a globally attracting stable periodic orbit. Despite a strongly negative Lyapunov exponent, a small amount of noise can introduce fluctuations of the period length. It is shown that this is a reasonable model for the observed dynamics of a bubble formation experiment in a heated capillary embedded in boiling water.

Journal Article↗
PubMed1982

Sudden large and periodic changes in heart rate in healthy young men after short periods of exercise.

The instantaneous heart rate and respiratory pattern were recorded immediately after brief periods of exercise in 41 healthy male students. Recordings were taken with the subjects both supine and standing. More than half of these subjects showed oscillatory heart changes when recovering supine but not when standing. During these oscillations the heart rate slowed suddenly by more than 30 beats/min; the oscillations had a period of 4 to 8 seconds, and they continued for half to two minutes. The P waves of the electrocardiogram were decreased during the slowing, consistent with increased vagal activity. When these oscillations occurred they each followed the start of an inspiration with the same latency as in respiratory sinus arrhythmia; unlike respiratory sinus arrhythmia, however, they did not occur after every inspiration but varied from 1:1 to 1:3 oscillations:breaths. They were not usually stopped by breath holding but were reduced or abolished by procedures which reduced venous return. This pattern of oscillations--"vagushalt"--seems to be different from respiratory sinus arrhythmias, and central venous pressure may contribute to the phenomenon. Although it is not widely recognised, vagushalt is probably very common and possibly its occurrence may change in disease.

Adolescent↗